Symmetrical magnetic deflection system



y 1954 A. D. M COMAS, JR 2,684,455

SYMMETRICAL MAGNETIC DEFLECTION SYSTEM Filed June 13, 1952 4Sheets-Sheet 1 FIG. I

INVENTOR. ARTHUR D. MCCOMAS JR.

A TTOR July 20, 1954 A. D. M coMAs, JR 2,684,455

METRICAL MAGNETIC DEFLECTION SYSTEM 5- A glv s y 1954 A. D. M coMAs, JR2,684,

SYMMETRICAL MAGNETIC DEFLECTION SYSTEM Filed June 13, 1952 4 heets-Sheet4 INVENTOR. ARTHUR D. MCCOMAS JR.

MW, QZIZLZMG ATTORNE S Patented July 20, 1954 UNITED STATE SYMMETRICALMAGNETIC REFLECTION SYSTEM Arthur D. McComas, J12, Cockeysville, M11,as-

signor to Bendix Aviation Corporation, Towson, Md, a corporation ofDelaware Application June 13, 1952, Serial No. 293,479

13 Claims.

This invention relates generally to electromagnetic deflection systemsfor cathode ray tubes and more particularly to improved arrangements ofsuch systems which provide novel disposition of the deflection coilsaround the neck of a cathode ray tube to provide improved deflectioncharacteristics.

Prior art electromagnetic deflection systems have been arranged invarious ways to provide uniformity of operation between the pairs ofcoils making up the orthogonal deflection system. The coils of theseprior art systems have usually taken the form of cylindrical coil pairsorthogonally disposed or have been similar to a progressive lap windingin the manner used in the stators of rotating machines. In all suchprior art arrangements, however, eflicient deflection has required thatthe coils providing the magnetic deflecting field in one direction beplaced closer to the ments of the stationary coils the coupled impedanceto the rotating coil is not independent of the rotational positionthereof. The resultant variation of the relative impedance of theorthogonal deflection coils introduces nonlinearities in the deflectionof the cathode ray which detracts from the utility of the display.rotating and stationary yoke combinations made in accordance with thepresent invention overcome this limitation and provide coupled impedanceefiects which are independent of the relative position of the two yokes.Furthermore, the symmetry of the stationary yokes herein describedprovide improved deflection systems generally, due to the simplifieddriver circuits which may be used with such identical load devices andthe improved deflection characteristics resulting from identicaldeflection force generating means for both deflection axes. With themethods of the present invention a high order accuracy of the magneticaxis of the coil pairs and of the angle between the axes of thedeflection coordinates may be obtained by spiral adjustment ofindividual coils in both deflection pairs inwardly or outwardly asrequired.

Accordingly, it is the primary object of the present invention toprovide an orthogonal electromagnetic deflection system having bothpairs of coils symmetrically arranged with respect to the cathode raytube upon which they are placed.

Another object is to tem employing deflection coils which are arrangedwith ccrresponding portions underlapping and overlapping adjacent coilsin the deflection system.

A further object is to provide a deflection system having a closedspiral coil arrangement for equalizing the effective winding diametersof the coils of the system.

Another object is to provide multiple sets of spirally arranged coilsfor use in balanced driving systems and the like.

Another object is to provide spirally arranged coils in a deflectionyoke with the windings thereof distributed to obtain magnetic fieldshaving desired characteristics.

A further object is to provide sets of spirally arranged deflectioncoils which are oppositely directed for obtaining desired control of themagnetic field produced thereby.

Another object of the present invention is to provide a closed spiralfixed deflection coil system in combination with a concentric rotatingcoil deflection system for equalizing the coupled impedancetherebetween.

A further object is to provide a combination rotating and fixeddeflection coil system capable of producing a desired deflectionirrespective of the rotational position of the movable coil for highsweep speeds.

A further object is to provide a new and improved method of sub-assemblyfor individual coils from an orthogonal pair deflection system such thatthe criticality of the final assembly of the orthogonal pair is greatlyreduced.

Still another object is to provide an improved method of aligning thespiral coils of a plural axes deflection yoke for a predeterminedrelation.

These and other objects of the present invention are accomplished with adeflection yoke made up of orthogonal deflection coil pairs which areapproximately semi-cylindrical in shape and which are mounted ofi-setwith respect to the axis of the cathode ray tube with which they areused with a substantially equal amount of underlap and overlap betweenadjacent coils of the two pairs. Yokes constructed in this manner may beemployed as stationary orthogonal deflection systems or combined withconcentric rotating yokes for combined signal displays. 7

The invention may be better understood by reference to the followingdetailed description taken in conjunction with the accompanying drawingswherein:

Fig. 1 is a perspective View of four adjacent coils formed into adeflection system of the present invention;

Fig. 2 is a sectional view taken in the vertical plane through the line2-2 of Fig. 1;

provide a deflection sys- Fig. 3 is an end elevational view for abalanced pair deflection system in accordance with the invention;

Fig. 4 is a View in the natiu'e of a developed winding diagram showingthe coils of Fig. 3 laid flat to illustrate the connections therebctweenand including an enlarged view of one coil;

Fig. 5 is an end elevation showing a double deflection yoke inaccordance with the present invention with oppositely directed spirals;

Fig. 6 is an end view of one pair of coils from each deflection systemshown in Fig. 5 with representation of the component and resultantmagnetic fields produced thereby;

Fig. 7 is an end elevation view of a fixed spiral deflection system witha rotating concentric pair of deflection coils;

Fig. 3 is a plan view of an arrangement for practicing the method oforthogonal sub-assembly of the invention;

Fig. 9 is a diagram useful in explaining the method of Fig. 8;

Fig. 10 is a plan view of an arrangement for practicing the method ofaligning all of the coils of a spiral yoke; and

Fig. 11 is a sectional view of a pair of deflection coils with amodified winding distribution.

Referring now to Fig. 1, there is shown a pair of vertical deflectioncoils H, l2 and a pair of horizontal deflection coils l'3', I l. Theindividual coils H-M may be wound in any of the well known distributedarrangements for producing a desired distribution of the fieldtherebetween. For simplicity of manufacture the individual coils may bewound and formed with a true semi-cylindrical inner contour, although itwill be apparent that a true or approximate spiral inner contour may beemployed, if desired. With the cylindrical construction of the coilsH-i-4, the assembly, in accordance with the present invention, is madelayoff-setting the coils of a pair by an equal amount in oppositedirections with respect to the axis of the cathode ray tube upon whichthey are to be placed. A cylindrical container IE! or other suitableprovision for supporting the coils in this manner is provided and thecoils may then be secured thereto by suitable means with approximatelyan equal amount of underlap and overlap between adjacent coils. As isshown in Fig. 1, coil is underlaps coil H and overlaps coil I2, coil Hunderlaps coil l4 and overlaps coil 1-3, coil 14 underlaps coil 12 andoverlaps coil II, and coil l2 under-laps coil [3 and overlaps coil f4.

Referring to Fig. 2' the arrangement of the coils IIM with respect tothe neck of a cathode ray tube [5 will be apparent. With thisarrangement the coil pairs H, H and 13, Himay be energized in anyconventional manner to pro" vide an orthogonal deflection system, theperformance of which will be that of one having equal effective windingdiameters for each pair of coils; The substantially completeencirclement of the tube [5 by each pair of coilspermitsmaximumdeflection sensitivity without introducing dissymmetry of the coilarrangement.

In Fig. 3, there is shown a deflection system which is essentially adouble set of windings arranged in spiral relation, generally similar tothe single set shown in Fig. 2. The vertical deflection system has innerwindings t6, IT and outer windings I8, i9 and the horizontal deflectionsystem has inner windings 2|. 22 and outer windings 23, 24, all havingthe underl'ap and overlap relation of the present invention with respectto adjacent coils and the inner and outer sets being arranged to spiralin the same direction. This multiple set of windings is useful, forexample, in obtaining push-pull operation of the deflection system, theconnections for which may be best seen in Fig. 4. The whole assembly maybe impregnated between the outer container I0 and an inner container 26*with a setable compound to provide a rugged structure and maintain therelative orientation of the coils.

Fig. 4 shows a yoke similar to that of Fig. 3 as it would appear if thevarious windings were peeled away from their assembled positions andlaid fiat along the deflection axes with the outer set of coils placedfarthest from the cathode ray tube 15. One connection which is suitablefor using the windings iii-24 in push-pull operation is shown. All ofthe winding pairs are returned to a common supply source terminal 25.From the supply terminal 25. the coils i5, {'1 are serially connected toprovide a north deflection pair, and coils ['8 I9 are serially connectedto provide a south deflection pair. In like manner, coils 21, 22 areserially connected from the source 25 to provide an east deflection pairand coils 23, 24 are serially connected fora west. deflection pair. Inthe operation of the system. of Fig. l, the terminals N, S may be drivenin push-pull to provide a north-south deflection and the terminals E. Wmay likewise be driven in push-pull to provide the east-west deflection.In such a system the deflection sensitivities of the outer coils may beadjusted to equal that of the corresponding inner pair of coils toobtain equal deflection sensitivities in opposite directions. Thesensitivity adjustment could be achieved, for example, by providing anincreased number of turns on the outer pair of coils l6, l9 relative tothe inner pair i6, t1 and a corresponding adjustment for the E, VJ axiscoils. The coil i8 is shown enlarged with a cosine distribution of the:separate hanks 3d of the coil: winding for providing a uniform. fielddistribution: and is representative of the construction which. ispreferably used for the coils l"l--24.

In Fig. 5 a deflection yoke construction is shown having orthogonalpairs 26 which spiral outward in a clockwise direction surrounded by aset of orthogonal deflection coils 2'5 which spiral outward in acounterclockwise direction. The orthogonal deflection axes individual tothe two sets are substantially symmetrical and the resultant field fromthe two sets is such as to produce cancellation of undesired components,as will be more fully described with reference to Fig. 6.

In Fig. 6 one pair of coils 26 and one pair 2'! of the oppositelyspiraling deflection coil sets of Fig. 5 are shown. The oil-set orspiral arrangements of the coils 26 is such as to produce a magneticfield represented, for purposes of illustration with exaggeratedcurvature, by flux lines 28. The magnetic field produced by the coils 27has oppositely directed flux lines 29. The resultant field from thesetwo-components has flux lines 3 l which may be had with any desireddegree of uniformity or' other desired field configuration by properlypositioning and proportioning the coil pairs 26, '21. Localized magneticflux 32 due to the end effect of the configuration of the coils 26 issubstantially eliminated by a like opposite end effect flux 32" producedby the coils 21. In practice, it will generally be found possible toarrange the single direction spiral coil configuration of the presentinvention to produce satisfactory results without noticeable distortiondue to the end effect flux 32. For example, for uniform fields thedistribution of windings in the individual coils may be proportionedwith the turns in the outward half slightly compressed with respect tothe geometrical axis of the coil, as hereafter described with referenceto Fig. 11. For extremely precise displays, however, or in specialapplications where some particular oleflecting fields are desired, theoppositely spiraling correction of end effect flux may be employed. Whenso used, the four windings 26, 21 of Fig. 6 may be all seriallyconnected and the number of turns in the windings 21 increased relativeto the number in the windings 26 to provide equal deflectionsensitivities or such ratio as is desired.

Referring now to Fig. '7, there is shown a stationary closed spiral yokecomprising a horizontal deflection pair 33 and a vertical deflectionpair 34, together with a conventional rotating concentric pair ofdeflection coils 35, all positioned around the cathode ray tube IS. Therotating coils 35 may be energized, for example, by slip rings. Rotatingand fixed deflection coil combinations are useful for ofl center sectordisplays or, for example, in combined automatic direction finder radardisplays, wherein a directional indication of a particular aircraft iscombined with a rotatable indication such as a planposition indication.In such displays used heretofore, it has been found that the impedancecoupled between the rotating coil from the stationary coils varies withthe relative position thereof.

For indications which are produced from a resultant deflection of therotating and the orthogonal stationary coils, this condition producesnonlinearities because of the different impedances in the stationarypairs caused by the unsymmetrical coupling of impedance between thesecircuits and the coils 35. These unequal impedances cause the currentsin coil pairs 33, 34 to be unequal, thus producing the undesirednon-linearity. This effect is especially objectionable for fast sweeps.With the arrangement as shown in Fig. 7 however it has been found thatthe impedance coupling between the coils 35 and each of the pairs 33, asis substantially constant and independent of the rotational position ofthe coils 35 and hence the aforementioned non-linear deflection iseliminated.

The method of sub-assembly of coils will be described with reference toFig. 8, where a schematic arrangement for the sub-assembly of adjacentcoils 35, 3? is shown for use with a corresponding pair, not shown, tomake an orthogonal yoke. The coils 36, 31 are movably arranged upon acam cylinder All which supports them in a manner identical with a finalfour coil assembly. Obviously, an assembly of four coils, two of whichwould be dummy coils, similar to that ofFig. 10 could be used topractice the method. of adjacent coil alignment to eliminate the needfor the specially shaped cam cylinder 4%. The coils 36, 3? arepositioned around a pair of crossed loops 38, 39 which have previouslybeen fixed in accurate orthogonal relation by well known null signalmethods. Upon energization of the coil 38 from a signal generator 45 thecoil 36 is moved until a null signal appears at the terminals thereof asmeasured by a high impedance voltmeter 46. The signal generator 45 isremoved from the coil 38 and connected to the coil 39, whereupon thecoil 31 is moved until a null signal is measured by the meter 46 at thethereof are perpendicular to each other.

terminals thereof. Ganged switching means 41 may be provided tofacilitate the required changes in circuit connections. Theseadjustments may be repeated if desired and the coils 3B, 3! are thenpermanently secured in the relative position thus established, accordingto any of the well known coil manufacturing techniques. The method justdescribed provides sub-assembly pairs of coils 36, 37 which may becombined. with a similar pair adjusted in the same manner to form any ofthe deflection yokes of the present invention. The final assembly ofthese pairs will produce an orthogonal deflection system withoutextremely accurate alignment of the opposite fixed sub-assembly pairs,as will be ap parent from the description of Fig. 9.

In Fig. 9 the sub-assembly of coils 36, 3'1 is positioned upon acylindrical support 20. The coil 3% will produce a magnetic field havingaxis 35 and the coil 3'! will produce a field having a magnetic axis 31and these axes 36, 3'! are perpendicular as a result of the previouslyperformed sub-assembly method described in connection with Fig. 8.Another fixed sub-assembly of coils 4!. 42 located approximatelyopposite the coils 36, 3'1 on the support 29 will produce magneticfields having orthogonal axes 4i and 42. Upon energizing the coils 38and 42 in series, the magnetic fields 36 and d2 combine to produce amagnetic field axis t3. Similarly energizing coils 3i and 4! in seriescombines the magnetic field axes 3i and M to produce a magnetic fieldhaving an axis 54. These resultant magnetic fields l3 and M areorthogonal and provide orthogonal deflection forces for the oathode raytube with which the yoke, comprising coils 35, 37, M, 42 mounted on thesupport 20, is used.

In Fig. 10 an arrangement is shown which is similar to that of Fig. 8,except that it is arranged for adjustment of both sets of coils of adeflection yoke. For this purpose the perpendicular loops 38, 39 arepositioned inside a cylindrical shell t8. Upon the outer surface of theshell 48, a set of coil pairs d9, 56 is arranged in interleaved relationas herein described. Connections are provided for selectively connectingthe signal generator 45 to the loops 38, 3E and voltmeters 46, 45' tothe individual coils of the pairs 50, 48 by means of ganged switchesiii. With this arrangement and with the switches 55 in the positionsshown, the loop 39 is energized and the voltages induced in the coils323 are measured by the voltmeters 46, t5. The coils 49 are bothadjusted spirally to obtain null readings on the voltmeters 46, 45 andthe switches 5! are reversed. The loop 33 is then energized and thecoils 56 are adjusted to obtain null voltages. These steps may berepeated, if required, until null conditions obtain in the respectivecoils for either switch position without further adjustment. The coilsare then secured in their adjusted relative positions with a suitablebinder or adhesive and assembled into a finished yoke of the type shownin Fig. 2. Yokes adjusted by this method, in addition to having themagnetic axes of the pairs 49, 58 orthogonal, achieve a high order ofcolinearity of the fields of the individual coils of the pairs. In otherwords, the fields of the coils 49 approach colinearity as do the fieldof the coils 50 and the resultant fields The optimum adjustment of bothof these characteristics is thus readily accomplished. I

As hereinbefore described, uniform turn distributions in individualcoils may be employed or such variants as the cosine distribution or thelike. For compensating the different spacing from the axis of thecathode ray tube E5 of the turns on the inner and outer portions of aspiral coil, the distribution of such turns may be varied in any desiredmanner. In Fig. 11, for example, there is shown a tube [5 with a pair ofspiral coils 52, 53 disposed in accordance with the present invention.The hanks 5 55, 55 (groups of turns) make up coil 52 and the hanks 5'5,58, 59 make up coil 53 and the distribution thereof is approximatelycosinusoidal with respect to the center of the coils. The departure froma true cosine distribution is shown by the displaced positions of theportions of hanks 55, 55 and 58, 59 on the outer portion of therespective coils 52 and 53 with respect to the indicated positions 55',55 and 58', 53' thereof for a true cosine distribution. The distributionin this case locates the hanks on the coils 52, E3 in the positionscorresponding to symmetrical angular projections from the center of thetube i5. This shaped distribution of the outer hanks constitutes aneffective cosine distribution with respect to the tube 55 for the spiralcoil arrangement.

Many variations and modifications will be apparent to those skilled inthe art in the light of the above teachings and are to be understood asbeing within the scope of the present invention.

What is claimed is:

1. An electromagnetic deflection yoke for a cathode ray tube comprising,a first pair of deflec-tion coils arranged for positioning on oppositesides of said tube, and a second pair of coils similarly arranged forpositioning on opposite sides of said tube, the magnetic axes of saidpairs being substantially perpendicular and each of the coils in a pairrespectively overlapping one and underlapping the other or the coils ofthe other of said pairs.

2. A cathode ray tube deflection system comprising, a coil assemblyhaving pairs of essentially diametrically opposed windings, each of saidwindings overlying a portion of one underlying a portion of the other ofthe windings peripherally adjacent thereto, and means for supplyingdeflection currents to said pairs.

3. A deflection coil assembly comprising, two pairs of essentiallydiametrically opposed wind-- ings, the magnetic axes of said pairs beingsubstantially perpendicular and each of said windings overlyiir aportion of one and underlying a portion of the other of the windingsforming the one of said pairs diverse from said each Winding.

4. A deflection system comprising, a coil assembly accordance with claim3 encircled by a similar assembly in accordance with claim 3, themagnetic axes of said assemblies being substantially aligned, and meansfor energizing corresponding pairs of coils in said assemblies inpushpull signal relation, the outward progression of all coils in saidassemblies having the same sense,

5. The system according to claim 4 in which the coils of the outsideassembly have a greater number of turns than the corresponding coils ofthe inside assembly, whereby the deflection sensitivities ofcorresponding coil pairs is equalized.

6. A deflection coil assembly in accordance with claim 3 encircled by asimilar assembly in accordance with claim 3, the magnetic axes of saidassemblies being in approximate alignment and the outward progression ofthe coils in. one assembly being of opposite sense to that of the. otherassembly.

'2. A deflection system comprising, a coil assembly in accordance withclaim 6, and meansfor serially energizing corresponding pairs of coilsin said assemblies.

8. A deflection assembly comprising, an assem-- bly in accordance withclaim 3, and a pair of diametrically opposed deflection coilsmounted forrotation about the longitudinal axis of said windings.

9. A deflection coil assembly comprising, first and second pairs ofapproximately semi-cyclindrical coils, the coils of each pair being inconcave opposition with said opposition being slightly ofi-set, andmeans positioning said pairs with the magnetic axes thereofsubstantially perpendicular and the coils of said pairs interleaved suchthat any coil of a given pair is partially inside of one coil andpartially outside of the other coil of the pair diverse to said givenpair and the remaining coil of said given pair is partially inside saidother coil and partially outside said one coil.

10. A deflection assembly comprising, an assembly in accordance withclaim 9 and a pair of diametrically opposed coils mounted for rotationabout the approximate mean longitudinal axis of said semi-cylindricalcoils.

11. The assembly according to claim 10 and including sliding contactmeans for energizing said rotating coils.

12. A deflection coil assembly comprising, first and second pairs ofapproximately semi-cylindrical coils of substantially equal size, thecoils of each pair being in concave opposition with said oppositionslightly oii-set, and means positioning said pairs with the magneticaxes thereof substantially perpendicular and the coils of said pairsinterleaved such that any coil of a given pair is partially inside ofone coil and partially outside of the other coil of the pair diverse tosaid given pair and the remaining coil of said given pair is partiallyinside said other coil and partially inside said other cell andpartially outside said one coil.

13. A cathode ray tube deflection system comprising, stationary flrstand second pairs of essentially semi-cylindrical coils, the coils ofeach pair being in concave opposition on opposite sides of the centralbeam axis of said tube and slightly off-set in opposite directions withrespect to said beam axis, said pairs being positioned with the magneticaxes thereof. substantially perpendicw lar and the coils of said pairsinterleaved such that any coil of a given pair is partially inside ofone coil and partially outside of the other coil of the pair diverse tosaid given pair and the remaining coil of said given pair is partiallyinside said other coil and partially outside said one coil, a pair ofcoils in concave opposition concentric with said axis and rotatablethereabout, and means for supplying deflection currents to saidstationary and said rotatable coil pairs.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,155,514 Tolson et a1 Apr. 25, 1939 2,243,893 Blumlein June3, 1941 2,395,736 Grundmann Feb. 26, 1946 2,420,156 Suchtelen May 6,1947

